This invention is directed towards a water treatment facility for removing contaminants from a water runoff stream, such as the type of stream which runs off of ground surfaces and streets. More specifically, the apparatus of the invention includes a separation vault which promotes the separation of particulate matter and contaminants from a water stream, prior to the water stream entering a river or water course.
As urban boundaries expanded worldwide, clarification of surface runoff was neglected. The water which now enters water ways contains contaminants which promote growth of undesirable organic matter in the water ways. Water ways are therefore slowed in velocity, particularly during low-flow periods, with a resultant deterioration in, or elimination of, aquatic animal life of a result of pollution. Surface runoff contains the remnant of fertilizers and detergents, such as phosphorous and excess nitrogen, heavy metals from vehicular exhaust systems, petroleum products from vehicles and machinery, and animal waste products. In small quantities, none of these contaminants would pose a significant problem, however, in densely populated urban areas, these contaminants are sufficiently concentrated to destroy desirable life forms in urban waterways and make such waterways unsafe for human recreation.
A number of know processes are available for separating particles from waste water. Such processes include gravity separators, a variety of parallel plate separators with or without coalescing filters, the use of chemicals as flocculent or poly-electrolytes, electric ionizing systems, air floatation systems, pressure filters and osmosis systems.
Flocculators are used to enhance particle growth of particle agglomeration and floc formation after chemical addition. Flocculation always occurs in two successive stage: perikinetic flocculation and orthokinetic flocculation.
Perikinetic flocculation is the particle growth or aggregation which results from random thermal motion of fluid molecules, known as "Brownian Movement." Perikinetic flocculation and coagulation generally take place in a microscale in less than one second.
Orthokinetic flocculation is particle growth or aggregation resulting from induced velocity gradients in the fluid. This type of flocculation occurs slowly in flocculators, usually requiring several minutes for complete floc formation. Orthokinetic flocculation is the usual mechanism used in potable, process and waste water treatment.
Traditional flocculators employ paddle mixers and baffles located in continuously stirred tanks. Short circuiting and back mixing occurs in these tanks, which results in an increase time for detention of the effluent in the holding tank while all of the effluent is treated.
While these systems have varying degrees of effectiveness, they all have certain deficiencies, not the least of which is the introduction of residual chemicals in the runoff stream. Other processes are not fully effective, and may not remove an adequate amount of contaminants found in the runoff stream.